For example, in the process of manufacturing semiconductor devices, a cleaning process is performed on a semiconductor wafer, as needed, to keep the surface of the semiconductor wafer clean. Jpn. Pat. Appln. KOKAI Publication No. 2003-168670 discloses a cleaning process of the single-wafer type, in which semiconductor wafers are processed one by one, as follows. Specifically, purified water is changed into mist by an inactive gas to obtain a fluid (i.e., a fluid of a so-called two-fluid type). The fluid thus obtained is supplied onto the surface of a semiconductor wafer, while the semiconductor wafer is rotated, to remove particles and so forth from the surface. Then, purified water is supplied onto the semiconductor wafer to perform a rinsing process thereon. Then, the semiconductor wafer is subjected to spin-drying.
However, this cleaning method increases the absolute value of static build-up voltage generated on the cleaned semiconductor wafer. Due to this voltage, the semiconductor wafer itself may be broken, or circuits formed on the surface of the semiconductor wafer may be damaged.